resending, now typing more carefully: *** Hey Xianqin, If it is a (bulk) alloy system, and if A-A and A-B are 1NN pairs, then, unless there is a phase transition or other perturbations that can involve chemical changes either within the sample of heterogeneous (say, nanophase formation of different composition) or homogeneous (say, ordering changes from random solid solution to an intermetallic compound, as in Au3Cu etc.) nature, the coord. numbers should stay the same. Thus, it is not physical to vary them independently. Thus, if the coord. number of the A-1NN is 12 (as in fcc) then set NB=12-NA and worry only if NA comes out to be outside the range between 0 and 12. Anatoly -----Original Message----- From: ifeffit-bounces@millenia.cars.aps.anl.gov [mailto:ifeffit-bounces@millenia.cars.aps.anl.gov]On Behalf Of XQ WANG Sent: Thursday, August 31, 2006 2:54 PM To: ifeffit@millenia.cars.aps.anl.gov Subject: [Ifeffit] Alloy EXAFS data fitting Dear all, I am trying to understand some EXAFS data collected on an alloy system (sorry I can't say it since these are not my data). It is a two-element alloy system, name AB. Their fitting results showed that A-B coordination number and A-A coordination number did not follow the similar trend with the temperature increase. I am just wondering if this case is possible? I had thought if A-A and A-B are from the same compound, they should follow the same trend. Maybe I am wrong. Another question is whether it is OK to combine coordination of A-A in A compound with CN of A-A in AB alloy if these two A-A bond distances are very close? If this case is OK, then combination of A-A CN and CN of A-B could follow differnt trend (I guess). But I thought we could not combine CN from different materials. Maybe I am wrong again?? Please let me know any suggestions concerning this situation. Thanks! Xianqin _________________________________________________________________ Check the weather nationwide with MSN Search: Try it now! http://search.msn.com/results.aspx?q=weather&FORM=WLMTAG _______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit